Immunologic studies were carried out on 4 patients with an unusual form of cutaneous leishmaniasis characterized by disseminated lesions, failure to respond to therapy and specific energy to the infecting organism. Blastogenesis to leishmanial antigens could be restored by removal of adherent suppressor cells. Most of these patients also had in vivo activation of B cells. One of the patients had an excellent response to controlled heat treatment. The serum of patients with filarial and schistosome infections was found to contain blocking activity to antigen-induced histamine release. The blocking activity had characteristics of IgG and was antigen specific. The demonstration of IgE in cord blood of Indian newborns was attributed to transplacental passage of IgE stimulated by filarial infection. Laotian refugee patients with a new form of schistosomiasis due to S. mekongi have been evaluated immunologically for the first time. Arrangements have been made to treat them with a new drug, pranziquantel. Immunologic studies were done before and after treatment with another new drug, oxamniquine. An improved radio-immunoassay was developed for detection of two polysaccharide antigens of schistosomes and antibody to them.